linux-kernel - Re: [PATCH v2] tracing: Fix memory leak in tracing_err_log

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Message-ID: <1561728902.9333.2.camel@kernel.org>
Date:   Fri, 28 Jun 2019 08:35:02 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     Takeshi Misawa <jeliantsurux@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tracing: Fix memory leak in tracing_err_log_open()

Hi,

On Fri, 2019-06-28 at 19:56 +0900, Takeshi Misawa wrote:
> If tracing_err_log_open() call seq_open(), allocated memory is not
> freed.
> 
> kmemleak report:
> 
> unreferenced object 0xffff92c0781d1100 (size 128):
>   comm "tail", pid 15116, jiffies 4295163855 (age 22.704s)
>   hex dump (first 32 bytes):
>     00 f0 08 e5 c0 92 ff ff 00 10 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<000000000d0687d5>] kmem_cache_alloc+0x11f/0x1e0
>     [<000000003e3039a8>] seq_open+0x2f/0x90
>     [<000000008dd36b7d>] tracing_err_log_open+0x67/0x140
>     [<000000005a431ae2>] do_dentry_open+0x1df/0x3a0
>     [<00000000a2910603>] vfs_open+0x2f/0x40
>     [<0000000038b0a383>] path_openat+0x2e8/0x1690
>     [<00000000fe025bda>] do_filp_open+0x9b/0x110
>     [<00000000483a5091>] do_sys_open+0x1ba/0x260
>     [<00000000c558b5fd>] __x64_sys_openat+0x20/0x30
>     [<000000006881ec07>] do_syscall_64+0x5a/0x130
>     [<00000000571c2e94>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Fix this by calling seq_release() in tracing_err_log_fops.release().
> 
> Signed-off-by: Takeshi Misawa <jeliantsurux@...il.com>
> ---
> Dear Steven Rostedt
> 
> Thanks for reviewing.
> 
> > Actually, I think it is safer to have the condition be:
> > 
> >         if (file->f_mode & FMODE_READ)
> > 
> > As that would match the open.
> > 
> > Can you send a v2?
> 
> I send a v2 patch.
> 
> Regards.
> ---
>  kernel/trace/trace.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 83e08b78dbee..4122ccde6ec2 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -7126,12 +7126,24 @@ static ssize_t tracing_err_log_write(struct
> file *file,
>  	return count;
>  }
>  
> +static int tracing_err_log_release(struct inode *inode, struct file
> *file)
> +{
> +	struct trace_array *tr = inode->i_private;
> +
> +	trace_array_put(tr);
> +
> +	if (file->f_mode & FMODE_READ)
> +		seq_release(inode, file);
> +
> +	return 0;
> +}
> +
>  static const struct file_operations tracing_err_log_fops = {
>  	.open           = tracing_err_log_open,
>  	.write		= tracing_err_log_write,
>  	.read           = seq_read,
>  	.llseek         = seq_lseek,
> -	.release	= tracing_release_generic_tr,
> +	.release        = tracing_err_log_release,
>  };
>  

v2 looks good to me, thanks for sending this fix.

Reviewed-by: Tom Zanussi <zanussi@...nel.org>


>  static int tracing_buffers_open(struct inode *inode, struct file
> *filp)